Precise Access\nto Ultrahigh-Molecular-Weight Polymers\nby Ylide-Functionalized Phosphine-Based Frustrated Lewis Pairs

Lewis\npair polymerization (LPP) is an advanced polymerization\ntechnique\nknown for its ability to synthesize ultrahigh-molecular-weight (UHMW)\npolymers under mild conditions with remarkable efficiency and precise\ncontrol. In this study, a strong electron-donor ylide-functionalized\nphosphine, (1-(diethylphosphanyl)ethylidene)triphenyl-λ<sup>5</sup>-phosphane (<b>YFP2</b>), is introduced as a Lewis base\n(LB). It is combined with a sterically hindered moderately acidic\nLewis acid (LA), (4-Me-2,6-<i><sup>t</sup></i>Bu<sub>2</sub>-C<sub>6</sub>H<sub>2</sub>O)Al<i><sup>i</sup></i>Bu<sub>2</sub> ((BHT)Al<i><sup>i</sup></i>Bu<sub>2</sub>), to\nprepare a frustrated Lewis pair (FLP) catalyst for the living methacrylates\npolymerization. The living character of this polymerization has been\nconfirmed through various key observations: successful chain-extension\nexperiments, a linear increase in the number-average molecular weight\n(<i>M</i><sub>n</sub>) of the polymer corresponding to monomer\nconversion and the ratio of monomer to initiator, and the development\nof distinct di- and triblock copolymers using different comonomer\naddition sequences. Importantly, this FLP catalyst system has successfully\nsynthesized UHMW poly(methyl methacrylate) (PMMA) with <i>M</i><sub>n</sub> values reaching up to 2935 kg/mol and narrow molecular\nweight distribution (<i>Đ</i>) at room temperature\n(RT). This achievement establishes a new record for the highest reported <i>M</i><sub>n</sub> for PMMA using a living/controlled LPP system.